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Why is the angle of deviation different for different colours?
Last updated on April 21st, 2023 at 04:05 pm
This post will cover why the angle of deviation is different for different colours. We will also see how the deviation angle, refraction angle, and refractive index are interrelated and all these again depend on the speed of light rays of different colours.
The angle of deviation is different for different colours – explanations
Light of all colors travels at the same speed in the vacuum. But in the other transparent medium, light rays of different colors are found to travel at different speeds because of their different wavelengths.
Let’s take an example of a glass prism. Here, lights of different colors (and different wavelengths) are found to have different speeds.
As lights of different colors have different speeds within the glass prism, therefore they have different values of refractive index(RI) in glass medium as well.
RI (µ ) for a specific colored light is inversely proportional to the speed of that colored light in that medium. [The RI formula here shows this relationship: µ = c / V, where c is the speed of light in a vacuum and which is constant.] See the list of RI formulas here.
µ = c / V, where c is the speed of light in a vacuum and which is constant
Now, consider the violet ray of light which has the least speed among all VIBGYOR colors.
A lower speed means a higher refractive index (see the above formula). Now higher refractive index denotes higher refraction or bending from the direction of the incident ray of light.
In other words, the refraction or bending of light is directly proportional to the refractive index.
Now as the RI gets larger, making the refraction more, this means a bigger deviation from the direction of the incident ray.
So bigger RI means a bigger deviation angle.
Now as the refracted ray is deviated by a bigger deviation angle, this means the refracted ray gets closer to the normal (perpendicular line on the refracting surface passing through the point of incidence). This means the refraction angle gets smaller.
So in a nutshell: using this formula µ = c / V Lower speed of a colored light => bigger RI => more bending or refraction =>bigger deviation and bigger deviation angle => smaller refraction angle (example Violet colored light) Higher speed of a colored light => smaller RI => less bending or refraction =>smaller deviation and smaller deviation angle => bigger refraction angle (example red colored light)
Read this Case Study: why is violet at the bottom of a spectrum
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The Physics: Our eyes can see many colors of visible light. Sunlight is a mixture of many colors together. Light from the sun looks white to our eyes. All of the colors are in white light, they are just all mixed up. To see all the colors separately, you can use a prism. A prism is a piece of glass or plastic in the shape of a triangle. The colors of the rainbow in order are: red, orange, yellow, green, blue, indigo, and violet. Many people remember this by the first letters that spell Roy G. Biv.
A prism works because the different colors of light travel at different speeds inside the glass. Because the colors of light travel at different speeds, they get bent by different amounts and come out all spread out instead of mixed up. Violet travels the slowest so it is on the bottom and red travels the fastest so is on the top. This is because what is called the index of refraction, (the ratio of the speed of light in a vacuum to the speed of light in a material), is increased for the slower moving waves (i.e. violet). The higher index of refraction means that violet light is the most bent, and red is then the least bent because of its lower index of refraction, and the other colors fall somewhere in between. When the air is full of water, like after a rainstorm, the water droplets act like a prism and can make a rainbow. Rainbows are circular in shape because the prisms (raindrops) that created them are spherical.
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Do different colors of light travel at different speeds?
Which of the following statements is correct regarding the propagation of light of different colors of white light in the air?
Red light moves fastest
Blue light moves faster than green light
All the colours of the white light move with the same speed
Yellow light moves with the mean speed as that of the red and the violet light
The correct option is C All the colours of the white light move with the same speed Dispersion: Dispersion occurs as a result of the varying degrees of refraction experienced by various colors of light. Different colors of light may travel at the same speed in a vacuum, but they may travel at different speeds in a refracting medium. The speed of violet light is slower than that of red light. Hence, option(C) is correct.
When white light is passed through a prism the different colors in the white light get refracted differently. Why does this happen?
Assertion :Different colours travel with different speeds in vacuum. Reason: Wavelength of light depends on the refractive index of medium. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion Assertion is correct but Reason is incorrect Assertion is incorrect but Reason is correct
We have c = ν λ ⟹ c ∝ λ i.e., the velocity of light of different colors is same in vacuum irrespective of the wavelengths. on entering any medium , the frequency does not change, but the wavelength and the speed of light changes. thus wavelength does depend upon the refractive index of the medium..
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REASON: n-Pentane and n-Hexane belong to the same class of hydrocarbons and they differ by a - C H 2 - group.
Assertion – The non-fusible impurities present in iron ore are removed by C a C O 3 .
Reason: C a C O 3 which decomposes into C a O and C O 2 . The C a O formed reacts with S i O 2 to remove silica
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The angle of deviation is different for different colours - explanations. Light of all colors travels at the same speed in the vacuum. But in the other transparent medium, light rays of different colors are found to travel at different speeds because of their different wavelengths. Let's take an example of a glass prism.
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Our eyes sense the different wavelengths and we see this as color. When white light enters the prism, each kind of light within white light (all the colors) are reflected at different angles because of the different wavelengths. ... When light travel through the air hits the prism, it changes its speed, and is thus enters the prism at a new ...
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283 1 2 8. One simple answer (and there are actual, deeper physics answers) is that the light interacts with the material, and those interactions are wavelength dependent. And, red light doesn't always travel faster than blue light - that is material dependent through those interactions mentioned above. - Jon Custer. Apr 3, 2015 at 14:08.
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can travel through a vacuum close vacuum A volume that contains no matter. such as in space travel at the same speed through a vacuum or the air Electromagnetic waves travel at 300,000,000 metres ...
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Feb 10, 2016. No. Photons travel at a constant speed (299,792,458 m/s) in a vacuum and in a medium. The wavelength of light does not affect the speed of light.
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All the colours of the white light move with the same speed. Dispersion: Dispersion occurs as a result of the varying degrees of refraction experienced by various colors of light. Different colors of light may travel at the same speed in a vacuum, but they may travel at different speeds in a refracting medium.
i.e., the velocity of light of different colors is same in vacuum irrespective of the wavelengths. On entering any medium , the frequency does not change, but the wavelength and the speed of light changes. Thus wavelength does depend upon the refractive index of the medium.